The present invention relates to blends of an elastomer, a processing oil, and a grafted resin component for use in air barriers.
Halobutyl rubbers, which are isobutylene-based copolymers of C4 to C7 isoolefins and a multiolefins, are the polymers of choice for best air-retention in tires for passenger, truck, bus and aircraft vehicles. Bromobutyl rubber, chlorobutyl rubber, and halogenated star-branched butyl rubbers can be formulated for these specific applications. The selection of ingredients and additives for the final commercial formulation depends upon the balance of properties desired—namely, processing properties of the green (uncured) compound in the tire plant versus the in-service performance of the cured tire composite, as well as the nature of the tire.
It is generally known that resins may be incorporated into air barrier compositions, see for example WO 02/48257, the prior compositions have generally used resins with higher glass transition temperatures, 50° C. or higher. Other background references include U.S. Pat. Nos. 4,413,067, 4,513,130, 5,246,778, 6,372,851, and EP 0 651 009 A. It is believed that the presently disclosed air barrier compositions containing non-aromatic processing oils in conjunction with a grafted resin component resin can be used in certain formulations to surprisingly improve air barrier qualities by decreasing the air permeability and brittleness temperature, while maintaining other desirable properties of the compositions.
U.S. Pat. No. 4,754,793 discloses a rubber composition comprising one hundred parts by weight of at least one butyl-type rubbery polymer; from about 3 to about 20 parts by weight of an aromatic hydrocarbon resin (α-methylstyrene homopolymer) having a softening point of about 93° C. to about 150° C. and a Tg of about 15° C. to about 75° C.; from about 30 to about 90 parts by weight of at least one carbon black, from 0 to about 7 parts by weight of hydrocarbon extender oil, and a curing system.
U.S. Pat. No. 4,113,799 discloses a carbon reinforced, partially cross-linked butyl rubber matrix sealant composition as described is particularly suitable for use as a self-healing tire puncture sealant. The sealant composition comprises a high average molecular weight butyl rubber and a low average molecular weight butyl rubber in a ratio of high to low molecular weight butyl rubber of between about 20/80 to 60/40, in admixture with a tackifier present in an amount between about 55 and 70 weight % of the composition. A partially hydrogenated block copolymer may be included in the admixture.
EP 0 314 416 A2 discloses a new rubber composition comprising from about 70 to about 90 parts by weight of a high molecular weight butyl-type rubbery polymer; from about 10 to about 30 parts by weight of a low molecular weight butyl-type rubber polymer, wherein the total amount of polymers described above is one hundred parts by weight, from about 30 to about 90 parts by weight of at least one carbon black, and a curing system.